Bacterial Diversity In Whitebacked Planthopper And Its Relationship With The Acquisition Of Southern Rice Black-streaked Dwarf Virus

Symbiotic bacteria have great effects on insect development, reproduction, survival and other biological characteristics. The whitebacked planthopper (WBPH), Sogatella furcifera Horvath, is one of the most serious insect pests of rice in Asia. Except sucking on rice plants, this pest can transmit southern rice black-streaked dwarf virus (SRBSDV). According to previous reports, there are two major symbiont bacteria in WBPH, Wolbachia and Cardinium, both of which have high infection frequency in natural WBPH populations. But it is not clear whether there are many other symbiotic bacteria in this insect, and whether the bacterial community diversity has relations with the transmission of SRBSDV. In this study, based on sequences of bacterial16S rRNA gene, we surveyed the bacterial community in three WBPH lines that received various antibiotic treatment and thus had different bacterial communities. Then, the three WBPH lines were compared in their capacity of acquiring/maintaining SRBSDV. Moreover, we detected and compared the density of Wolbachia and Cardinium between adults that acquired SRBSDV and those free of this virus.From the WBPH line sfu-W not receiving any antibiotic treatment, we identified a total of11bacteria that belonged to α-, β-, y-Proteobacteria, Bacteroidetes, Actinobacteria, and Bacilli. Wolbachia and Cardinium were the dominant bacteria, followed by Pantoea agglomerans. The bacteria community was dramatically different in both gentamicin-and tetracycline-treated WBPH lines (named sfu-G and sfu-T, respectively) as compared with sfu-W, with the density of Wolbachia and Cardinium declined in the line sfu-T. Fifteen and34bacteria were identified in the sfu-G and sfu-T, respectively, but some bacteria increased in abundance. After being incubated on SRBSDV-infected plants for2wk, the frequency of individuals acquiring SRBSDV was lower in sfu-T and sfu-G lines than in sfu-W, suggesting that the SRBSDV transmission capacity of this insect might have some relations with bacteria community. But Wolbachia and Cardinium did not have any detectable relationship with the SRBSDV transmission. The density of Wolbachia in WBPH increased after being infected with SRBSDV. The results showed that the SRBSDV transmission by WBPH has certain relations with symbiotic bacteria, and changes in bacteria community would affect virus transmission capacity. On the other hand, acquisition of the virus has the possibility of leading an increase in Wolbachia density. These results will help us to understand the mechanisms of SRBSDV transmission, and enrich our knowledge on the relationships between plant virus and symbiotic bacteria in vector insects.